The adjustment of the flow of liquids and/or gases in coffee machines can serve, on one hand, to shut off and on the other to channel liquids or gases to certain functional units or pouring spouts. Depending on the valve position, for example, it is possible to feed hot water to a pipe for broth or steam to a steam pipe. In higher quality coffee machines, ceramic valves are used to regulate the quantity of liquids, in which an adjusting disk fitted with an outlet aperture is turned according to the chosen preparation, so that the outlet aperture forms a flow channel together with the inlet and outlet pipes.
Tube valves are well-known devices for the discharge of steam. They consist of a conduit through which liquid or gas is led and a pinch jaw which squeezes the conduit in such a way that its inner diameter is reduced. The flow rate and indirectly also the flow pressure is thereby adjusted.